The application generally relates to a control system for a compressor. More specifically, the application is directed to controlling the output capacity of a compressor based on the outdoor ambient temperature.
Many traditional heating, ventilation and air conditioning (HVAC) systems can operate with a single speed compressor and deliver 100% of the compressor's possible output capacity at all times regardless of the amount of cooling required for the system (cooling load). HVAC systems can be rated for system capacity and Energy Efficiency Ratio (EER) at a 95° F. outdoor ambient temperature condition as required by industry standards and government regulations. HVAC systems can also be rated for Seasonal Energy Efficiency Ratio (SEER) at an 82° F. outdoor ambient temperature condition. Some HVAC systems may modulate the output capacity of the compressor to reduce the compressor capacity at the 82° F. outdoor ambient temperature condition or point to more effectively match or correspond the output capacity of the compressor to the cooling requirement of the HVAC system and thereby improve the SEER rating. However, an HVAC system that modulates capacity at the 82° F. outdoor ambient temperature point may still rate the system capacity and EER at 100% of the available compressor output or capacity at the 95° F. outdoor ambient temperature point.
As discussed above, HVAC systems are rated for capacity and efficiency at a 95° F. outdoor ambient temperature condition. However, HVAC systems are also required to provide cooling at outdoor ambient temperature conditions of 115° F. or higher. Since the output capacity of the compressor is greater at 95° F. than at 115° F., and the compressor capacity is rated at 100% output, the capacity output of the compressor at the 95° F. temperature condition can exceed the load requirement for the HVAC system, which results in less efficient operation of the HVAC system.
Therefore, what is needed is control systems and methods for a compressor to permit the compressor to operate efficiently at the 95° F. outdoor ambient temperature point while still having sufficient available capacity to satisfy load requirements for the HVAC system at higher outdoor ambient temperatures, i.e., greater than 95° F.